I use Windows (XP with Activestate 5.10.1) all the time for my Perl development. I believe when Windows gets a program name without extension (your example was 'perl'), the 'search' is similar to the following pseudo-code:

That is to say, search the local directory first, even if it isn't in your path (you won't see '.' when you type 'path' from cmd.exe). Try appending each extension in the %PATHEXT% environment variable to the program name and search current directory followed by each directory in your path.

This is *WAY* beyond Perl scope, but a nifty batch file I found and modified (I would give credit if only I remembered where I found this, Google 'which.bat' and a few different sites with different versions of this come up) acts much like the 'which' command on Unix. Save as 'which.bat' and put it in a directory in your %PATH% environment variable.

@echo off
setlocal
REM
REM Help
REM
if {%1}=={/?} goto HELP
if {%1}=={--help} goto HELP
REM
REM Check args
REM
if {%1}=={} goto SYNTAX_ERROR
if not {%3}=={} goto SYNTAX_ERROR
REM
REM Start Get ARGS
REM
:ARGS
if {%1}=={} goto EXECUTE
set string=%1
REM
REM If the first character in arg is a -, it's a switch
REM
if "!string:~0,1!"=="-" (
set position=0
:LOOP
REM
REM If the character indicated by the string is a space, ech+o a return;
REM else, just echo the character
REM
if "!string:~%position%,1!"=="" goto SLIDE
if "!string:~%position%,1!"=="a" set WHICHALL=YES&& goto INCR
if "!string:~%position%,1!"=="-" goto INCR
echo %0: unknown option -- "!string:~%position%,1!"
:INCR
REM
REM Increment the position in the string and loop
REM
set /a position=%position%+1
goto LOOP
) else set batchparams=%1
:SLIDE
shift
goto ARGS
REM -------------------------------------------------------
:EXECUTE
set errorlevel_=0
set program_=%batchparams%
:: Any input with wildcard or path characters is a syntax error.
for /F %%i in ('echo ":" ^& echo "\" ^& echo "*" ^& echo "/" ^& echo "+?" ^& echo "," ^& echo ";"') do (
echo %program_% | find %%i > nul && goto SYNTAX_ERROR
)
:: This variable stores the current directory, followed by PATH, as
:: the search order to search for program files. Quotes are added
:: between each ';' to handle paths with spaces.
set path_="%cd%";"%PATH:;=";"%"
:: Lowercase the path extensions. This is needed to perform
:: case-insensitive extension comparisons.
set path_ext_=%PATHEXT%
set path_ext_=%path_ext_:A=a%
set path_ext_=%path_ext_:B=b%
set path_ext_=%path_ext_:C=c%
set path_ext_=%path_ext_:D=d%
set path_ext_=%path_ext_:E=e%
set path_ext_=%path_ext_:F=f%
set path_ext_=%path_ext_:G=g%
set path_ext_=%path_ext_:H=h%
set path_ext_=%path_ext_:I=i%
set path_ext_=%path_ext_:J=j%
set path_ext_=%path_ext_:K=k%
set path_ext_=%path_ext_:L=l%
set path_ext_=%path_ext_:M=m%
set path_ext_=%path_ext_:N=n%
set path_ext_=%path_ext_:O=o%
set path_ext_=%path_ext_:P=p%
set path_ext_=%path_ext_:Q=q%
set path_ext_=%path_ext_:R=r%
set path_ext_=%path_ext_:S=s%
set path_ext_=%path_ext_:T=t%
set path_ext_=%path_ext_:U=u%
set path_ext_=%path_ext_:V=v%
set path_ext_=%path_ext_:W=w%
set path_ext_=%path_ext_:X=x%
set path_ext_=%path_ext_:Y=y%
set path_ext_=%path_ext_:Z=z%
:: If the program name has an extension, we want to verify that the
:: extension is one of those in the path_ext_ environment variable.
:: If it is, then this script will only search for that program with
:: that specific extension. If not, all of the extensions in the
:: path_ext_ variable will be tested, appended to the program name.
:: Get the extension if any from the program name.
for /F %%i in ("%program_%") do (set extension_=%%~xi)
:: Comparing the program extension against the list of executable
:: extensions. If the extension is found, then path_ext_ will just
:: have that extension.
set path_ext_=%path_ext_:;= %
if not {%extension_%}=={} (
for %%i in (%path_ext_%) do if "%%i"=="%extension_%" (
set path_ext_=%extension_%
for /F %%i in ("%program_%") do (set program_=%%~ni)
)
)
:: This will prepend a path prefix to the program name and append an
:: executable extension for every path and extension found in the
:: path_ and path_ext_ variables.
for %%i in (%path_%) do (
for %%j in (%path_ext_%) do (
if exist "%%~i\%program_%%%~j" (
set found_=%%~i\%program_%%%~j
if {%WHICHALL%}=={YES} echo !found_!
if not {%WHICHALL%}=={YES} goto FOUND
)
)
)
if "%found_%"=="" echo '%batchparams%' not found.
goto END
:FOUND
echo %found_%
goto END
:SYNTAX_ERROR
echo which: The syntax of the command is incorrect. 1>&2
goto ERROR
:ERROR
set errorlevel_=1
:END
exit /B %errorlevel_%
:HELP
echo.
echo %0 will find the program file that is used when run from
echo a DOS prompt. It will search the current directory and the
echo PATH environment variable directories for the program using
echo the extensions found in the PATHEXT environment variable.
echo.
echo USAGE:
echo.
echo %0 [options] ^<program^>
echo.
echo -a Print all matches in order; don't stop at first+.
echo.
echo program An external command, program, or script.
echo.
echo If you want to find a program with a particular extension,
echo include that extension in the program name and the 'which'
echo command will only search for a program file with that extensi+on.
echo.

When putting a smiley right before a closing parenthesis, do you:

Use two parentheses: (Like this: :) )
Use one parenthesis: (Like this: :)
Reverse direction of the smiley: (Like this: (: )
Use angle/square brackets instead of parentheses
Use C-style commenting to set the smiley off from the closing parenthesis
Make the smiley a dunce: (:>
I disapprove of emoticons
Other